Having a similar problem with my 2000 reg 1.9TDI. Putting the boot down produces nearly nothing with frequent clouds of black smoke. Car chuggs when taking off in 1st and 2nd gear also. Had 2 faults from scan - camshaft position sensor (g40): signal out of range and also Charge Pressure Control: negative deviation. I have cleared the codes and it the problem seems less apparent.
will be taking a look at the pipes from the intercooler as per other instructions here as well as checking out the MAP sensor.

This is a really good forum everyone! Learning lots and hopefully will be spending a little less time and $$$ dealing with the garages!